Wednesday, August 01, 2007

One of the joys of my summer is growing our own tomatoes (actually, growing our own tomatoes, cucumbers, zucchini, lettuce,...). This year, my dad bought us an heirloom 'Brandywine' tomato. We planted it along with the rest of our vegetables and have watched it flower and start to produce a number of robust fruit. It looked like many more flowers were on the way and so I was anticipating a bumper crop. But now, it looks like I'll be lucky to salvage the four fruits currently on the vine.

We have a tomato worm in our midst. Or at least, we did.

I hadn't been outside to check on the garden in the past few days, so I didn't know we had a Manduca quinquemaculata larvae munching away on our prized tomato plant. When I went out this evening to water, here's what I saw:

The entire top half of our 'Brandywine' was completely defoliated. I'd seen tomato worms before, so I knew what to look for - a large, green, and, admittedly, cool-looking caterpillar - so large and cool in fact that people's first reaction to them is usually, "Wow". Well, sure enough, there it was hanging onto a leaf just at the base of the damaged area - the bugger was working its way down the plant, towards the ripening fruit.

But, actually, this one wasn't really moving. In fact, it wasn't really doing anything. Just hanging there underneath a leaf. Not only that, but it looked different than the ones I've seen before. What are all those white things?

On closer examination, I had a pretty good idea what it was, at least in general. I'd run across this kind of thing in grad school, studying yucca moths (a tale for another day). Looks like our tomato worm had a bad case of the parasitoids. If I had to guess, I'd say some female wasp came by and laid her eggs inside the caterpillar. Once the eggs hatched, the wasp larvae ate their way out of the caterpillar to pupate, forming these white cocoons. Gross? Sure, but cool too.

A quick search on Google confirms it. Specifically, some species of braconid wasp appears to have parasitized (parasitoidized? parasitoided?) the moth larvae (or perhaps, even cooler, the moth eggs). The tomato worm is decidedly dead now - nothing more than a tomato plant ornament. An ornament housing hundreds of developing wasps that is.

So what do I do now? Well, I could remove the offending caterpillar carcass. But the caterpillar is no longer threatening my heirloom crop. So, I think I'll leave it be and wait for the wasps to emerge. If I'm lucky, I'll be able to get some photos. At the very least, I've got my very own biological pest control system in place. Tomato worms beware!

addendum: August 6th - After a weekend away, I went outside today to check if the wasps were emerging and found that the entire tomato worm carcass had disappeared. It, and the wasp cocoons, were just gone. I checked the ground around the tomato plant, thinking the caterpillar and passengers had succumbed to the force of gravity, but, alas, it was no where to be found. Not sure what could have happened to it - could some other critter have eaten it? In any case, there will be no photos of emerging Hymenoptera. :(

Yo ho ho!

"We must acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system--with all these exalted powers--Man still bears in his bodily frame the indelible stamp of his lowly origin."